| Study | Risk of bias for randomization | Risk of bias for concealment | Risk of bias for blinding | Risk of bias for incomplete data | Risk of bias for selective outcome reporting | Risk bias for other problems |
| Qi et al [18], 1996 | Uncertain | Uncertain | Low risk | Low risk | Low risk | Low risk | Liu and Gong [19], 2003 | Uncertain | Uncertain | Low risk | Low risk | Low risk | Low risk | Shen et al. [20], 2003 | High risk | Uncertain | Low risk | Low risk | Low risk | Low risk | Yu et al. [21], 2006 | Low risk | Uncertain | Low risk | Low risk | Low risk | Low risk | Hou [22], 2007 | Uncertain | Uncertain | Low risk | Low risk | Low risk | Low risk | Yao et al. [23], 2007 | Uncertain | Uncertain | Low risk | Low risk | Low risk | Low risk | Gao et al. [24], 2008 | Low risk | Uncertain | Low risk | Low risk | Low risk | Low risk | Li [25], 2008 | Uncertain | Uncertain | Low risk | Low risk | High risk | Low risk | Ye [26], 2009 | Uncertain | Uncertain | Low risk | Low risk | Low risk | Low risk | Long et al. [27], 2000 | Uncertain | Uncertain | Low risk | Low risk | Low risk | Low risk | Wu and Cui [28], 2001 | Uncertain | Uncertain | Low risk | Low risk | Low risk | Low risk | Xiao et al. [29], 2001 | High risk | Uncertain | Low risk | Low risk | Low risk | High risk | Deng [30], 2002 | Uncertain | Uncertain | Low risk | Low risk | Low risk | Low risk | Yang [31], 2002 | Uncertain | Uncertain | Low risk | Low risk | Low risk | Low risk | Zhao [32], 2002 | Uncertain | Uncertain | Low risk | Low risk | Low risk | High risk | Gao et al [33], 2003 | Uncertain | Uncertain | Low risk | Low risk | Low risk | Low risk | Hong et al [34], 2003 | Uncertain | Uncertain | Low risk | Low risk | Low risk | High risk |
Nian [35], 2003 | Uncertain | Uncertain | Low risk | Low risk | Low risk | Low risk | Zhang and Hong [36], 2003 | Uncertain | Uncertain | Low risk | Low risk | Low risk | High risk | Chen [37], 2004 | Uncertain | Uncertain | Low risk | Low risk | Low risk | Low risk | Chen et al. [38], 2005 | Uncertain | Uncertain | Low risk | Low risk | Low risk | Low risk | Peng [39], 2005 | Uncertain | Uncertain | Low risk | Low risk | Low risk | Low risk | Liu and Wang [40], 2006 | Uncertain | Uncertain | Low risk | Low risk | Low risk | Low risk | Yuan et al. [41], 2006 | Uncertain | Uncertain | Low risk | Low risk | Low risk | Low risk |
Ning et al. [42], 2007 | Low risk | Uncertain | Low risk | Low risk | Low risk | Low risk | Ma et al. [43], 2007 | Uncertain | Uncertain | Low risk | Low risk | Low risk | Low risk | Xiao [44], 2007 | Low risk | Uncertain | Low risk | Low risk | Low risk | Low risk | Yang et al. [45], 2007 | Uncertain | Uncertain | Low risk | Low risk | Low risk | Low risk | Cai and Wei [46], 2008 | Low risk | Uncertain | Low risk | Low risk | Low risk | Low risk | Cai [47], 2008 | Uncertain | Uncertain | Low risk | Low risk | Low risk | Low risk | Chen and Fan [48], 2008 | Uncertain | Uncertain | Low risk | Low risk | Low risk | Low risk | Liu [49], 2008 | Uncertain | Uncertain | Low risk | Low risk | Low risk | Low risk | Zhang and Chen [50], 2008 | Uncertain | Uncertain | Low risk | Low risk | Low risk | Low risk | Cai and Wang [51], 2009 | Uncertain | Uncertain | Low risk | Low risk | Low risk | Low risk | Chen and Ye [52], 2009 | Uncertain | Uncertain | Low risk | High risk | Low risk | Low risk | Su et al. [53], 2009 | Uncertain | Uncertain | Low risk | Low risk | Low risk | Low risk | Wang [54], 2009 | Uncertain | Uncertain | Low risk | Low risk | Low risk | High risk | Wang et al. [55], 2009 | Uncertain | Uncertain | Low risk | Low risk | Low risk | Low risk | Yu and Chen [56], 2009 | Uncertain | Uncertain | Low risk | Low risk | Low risk | Low risk | He et al. [57], 2010 | Low risk | Low risk | Low risk | Low risk | Low risk | Low risk | Wu and Li [58], 2005 | Uncertain | Uncertain | Low risk | Low risk | Low risk | Low risk | Li et al. [59], 2008 | Uncertain | Uncertain | Low risk | Low risk | Low risk | Low risk | Dong [60], 2008 | Uncertain | Uncertain | Low risk | Low risk | Low risk | Low risk | H. Shi and Q. Shi [61], 2009 | Uncertain | Uncertain | Low risk | Low risk | Low risk | Low risk | Shi and Jiang [62], 2009 | Uncertain | Uncertain | Low risk | Low risk | Low risk | Low risk | Lin and Wu [63], 2010 | Uncertain | Uncertain | Low risk | Low risk | Low risk | High risk |
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